DIVERSE ICHNOFOSSIL ASSEMBLAGES FOLLOWING THE P-T MASS EXTINCTION, LOWER TRIASSIC, ALBERTA AND BRITISH COLUMBIA, CANADA: EVIDENCE FOR SHALLOW MARINE REFUGIA ON THE NORTHWESTERN COAST OF PANGAEA
Bibliographic record
Abstract
Abstract Diverse and locally abundant Lowermost Triassic (lower Induan, Griesbachian) trace-fossil assemblages are described and their significance for the location and characteristics of western Pangean environmental refugia are assessed. Trace fossils within the Montney Formation in northwestern Alberta and northeastern British Columbia record the activities of a wide variety of marine invertebrates. Many forms represent the dwelling and feeding traces of allochthonous storm-transported colonizers. Anachronistic forms—more typical of Paleozoic than Mesozoic successions—including Cruziana, Diplichnites, Monomorphichnus, and Trichophycus, are common. Notably these Paleozoic holdovers, as well as Rhizocorallium, Thalassinoides, and Spongeliomorpha, were likely constructed by marine arthropods. Trace fossils are rare in both shallow water (upper shoreface and foreshore) and offshore depositional settings, but are abundant in offshore transition to distal lower shoreface depositional settings. Low diversity and low ichnofabric indices characterize autochthonous infauna in Montney offshore transition settings, whereas high diversity, low ichnofabric indices distinguish allochthonous infauna in the same settings. High diversity and high ichnofabric indices typify distal lower shoreface successions. Several lines of evidence, including diminutive trace fossils and low diversity of resident infauna in proximal-offshore settings, support the hypothesis of shallow marine anoxic to dysoxic conditions in the study area during the Griesbachian. This trace-fossil distribution, and the abundance of allochthonous faunas in the study interval, reflect an infauna whose distribution was limited by both wave-stressed proximal settings and oxygen-stressed distal settings, resulting in colonization of a very narrow habitable zone. High diversity of trace-fossil assemblages in the study interval suggests the presence of shallow marine refugia wherein organisms survived the extinction interval and weathered the adverse conditions that dominated the world's oceans during the lowermost Mesozoic. Mid- to high paleolatitude refugia, such as the Pedigree-Ring-Kahntah area, played a crucial role in both extinction survival as well as post-event recolonization of the world's oceans.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".